Latest Design of ILC （ RDR)

• 1.3 GHz technology developed by TESLA Collaboration, R&D from 1992 to reduce the cost per MeV by a factor of 20 from current SCRF installations (CEBAF).

• Increased the operating accelerating gradient by a factor of 5 : ~5 MV/m to ~25 MV/m,

Reduced the cost per meter by a factor of four for large-scale production.

• TESLA cavity R&D based on CERN, CEBAF (JLAB), Cornell University. KEK, Saclay and Wuppertal.

• Basic element of the technology is a nine-cell 1.3 GHz niobium cavity.

• Approximately 160 of these cavities have been fabricated by industry as part of R&D program at DESY.

A Primary Cost Driver for ILC -- Superconducting RF Technology

Principle of 50MV/m Cavity shape designs with low Hp/Eacc

TTF: TESLA shapeReentrant (RE): Cornell Univ. Low Loss(LL): JLAB/DESYIchiro ｰ Single(IS): KEK

TESLA LL RE IS

Diameter [mm] 70 60 66 61

Ep/Eacc 2.0 2.36 2.21 2.02

Hp/Eacc [Oe/MV/m] 42.6 36.1 37.6 35.6

R/Q [W] 113.8 133.7 126.8 138

G[W] 271 284 277 285

Eacc max 41.1 48.5 46.5 49.2

ICHIRO Cavity

Goal ： 51 MV/m

.

Fabricated Six ICHIRO Single Cells

• Electron Beam Welding (EBW)• Both KEK in-house machine and

industrial machine were used

• Six IS cavities were fabricated (IS#2, #3, #4, #5, #6, #7).

• Series of tests done to optimize KEK surface treatment.

Deep-drawn Nb cups

Stones and water

Rough stones Fine stones

KEK CBP• Rough stones + water : 4 hours x 3 times• Removal thickness = 25 μm x 3 = 75 μm

• Fine stones + water : 4 hours x 3 times• Removal thickness = 20 μm x 3 = 60 μm

• Total removal thickness = 135 μm.

Centrifugal Barrel Polishing (CBP) Mechanical Grinding

• Light Chemical Polishing (CP) HF(46%) : HNO3(60%) : H3PO4(85%) 1 :1 : 1 in volume

• CP for 1 minute at 25 OC.

• Removal thickness = 10 μm.

• Prepare smooth surface before EP.

• Annealing/Degassing in furnace

750 OC for 3 hours

• Degassing of hydrogen important.

• Temperature and time optimized for cavity softness and cost.

Light Chemical Polishing Annealing - Degassing

Measurement of and 0Q accE

0Q Unloaded Q-value

Measure time constant for cavity to “ringing down” when RF switched off

0loss

UQ

P

lossP

tP

rP

inP

LQ

0

1 1 1 1

in r tQ Q Q Q

accE Accelerating Field

2sh lossR V P

acc effV E d

acc sh loss effE R P d

0acc loss t tE Z Q P Z Q P tt

UQ

P

loss in r tP P P P

Geometric Factor

Schematic of Experimental Setup

Cavity in Cryostat

Signal Generator

Phase Locked LoopQ of Cavity is very large

Power Meters

1.9K LHe

Re-Entrant Cavity - Best Eacc = 59 MV/m

• Manufactured @ Cornell• Surface preparation at KEK• Vertical test @ Cornell

International Collaborations （ ILC WG5-Asia ）

Korea, PAL: Y. uk SOHN 　stayed Mar – Aug 2005 (WG5 Korea convener)

Korea, Pusan Univ: CHO (student)stayed in Mar 2005

IHEP: Shi Hua(engineer) stayedFeb - Mar 2005

Canada, Toronto Univ: Prof. Robert ORRstays from Aug 2005 for 1 year

LNL-INFN: Giullia LANZA(student) stays Jan – Mar 2006.

Korea, CHEP, Kyungpook Univ.: Prof. Hyoung Suk KIM stayed Jan-Mar 2006

IHEP: GE Mingqi(student) stayed Jan– Mar 2006